1. Field of the Invention
The invention relates to a perforator with a perforating disk rotatably seated in a U-shaped bearing bracket. The bearing bracket is moved into and out of the path of movement of a piece to be perforated by a piston-cylinder unit which can be actuated from either side. The piston-cylinder unit is housed in a fastening element which can be connected to a machine frame by guide bolts movably disposed in the bearing bracket which maintain the bearing bracket fixed against rotation in respect to the fastening element.
2. Description of Prior Art
A perforator of this type is disclosed in German Patent DE-PS 34 39 199. As disclosed therein, the fastening element is an open tray, the bottom of which is oriented towards the bearing bracket and which is closed on the side away from the bearing bracket by a cover. A commercially available piston-cylinder unit is used for displacing the bearing bracket with the perforating disk, which consists of a piston with a piston rod housed in a cylinder housing. This piston-cylinder unit is housed in the tray-shaped fastening element. Therefore the guide bolts for the bearing brackets must have a distance larger than the sum of the diameter of the cylinder housing and the diameter of the guide bushings for the bearing bracket. This establishes a minimum size for the perforator.
An object of the invention is to simplify the structure of a perforator of the previously mentioned type and to reduce the size of the perforator in the process.
This object is attained in accordance with the invention where a quadrate fastening element in the form of a cylinder has a blind bore extending from the side facing a bearing bracket, in which a piston, which is provided with seal rings, is sealingly guided in a displaceable manner. The blind bore is closed by means of a seal bushing through which extends a piston rod connected to a piston, which piston is connected to the bearing bracket. The blind bore transforms on the side facing the bearing block into an end section with a larger diameter forming a shoulder against which the seal bushing rests. In another embodiment the cylinder as a fastening element is plate-shaped and oriented to the plane of the perforating disk. A plate-shaped piston is displaceably guided in a quadrate sealed recess of the cylinder and is fixedly connected with the bearing bracket by a sealed piston rod displaceably guided in the cylinder. Both sides of the piston which extend crosswise to the displacement direction of the piston are provided with sealing elements which seal on all sides in the direction of the recess of the cylinder.
In this embodiment the fastening element forms the cylinder housing of the piston-cylinder unit and does not require a cover. It is possible to reduce the length of the two guide bolts of the bearing bracket so that the structural height of the perforator as a whole is reduced. The determining dimension for the length of the guide bolts in this embodiment is the diameter of the blind bore, which corresponds to the interior diameter of the cylinder housing of the known perforator, or the dimension of the quadrate recess in the fastening element as well as the diameter of the guide bushings of the guide bolts of the bearing bracket.
In accordance with an embodiment of this invention the seal bushing is fixed by a retaining ring in the end section of the blind bore and is maintained in contact with the shoulder, limiting the displacement path of the piston and providing the piston rod with additional guidance.
An absolutely straight guidance of the bearing bracket is attained where the guide bolts of the bearing bracket are guided in guide bushings, which are inserted into bores of the quadrate fastening element and are immovably held in the bores at both ends by retaining rings. The installation of the guide bushings is made easier and improved where the bores only extend over part of the thickness of the quadrate fastening element and, on the side facing away from the bearing bracket, transform into end sections with enlarged diameters in which are placed on the receptacle, the retaining ring for securing the guide bushings and are closed by a threaded plug.
Securing the perforator on the machine frame is achieved in a simple manner by the quadrate fastening element comprising a fastening clamp together with an L-shaped part formed of one piece with it, and the leg of the part facing away from the fastening element being provided with a through-bore to receive a fastening screw.
In accordance with one embodiment, the simple manufacture of the fastening element is made possible where the recess is in the form of an opening in the cylinder into which a rectangular tube section is sealingly seated as a piston guidance. The open front ends of the rectangular tube section tightly adjoin the facing sides of the recess in the cylinder. In accordance with a further embodiment of this invention, the free side walls of the rectangular tube section end flush with the facing sides of the plate-shaped cylinder.
In accordance with a further embodiment of the invention, the piston-cylinder unit is designed in such a way that the recess is in the shape of an opening in the cylinder and that after insertion of the piston into the recess the latter is tightly covered by means of two cover plates and the cylinder chamber for the piston is thus complemented.
In both cases it has been advantageously provided that the dimensions of the cylinder in the direction of the axis of rotation of the perforating disk correspond to the associated dimensions of the bearing bracket.
The two-sided actuation of the piston-cylinder unit is provided in a simple manner where the control lines for the piston-cylinder unit enter into the cylinder and end, in the area of the sides oriented crosswise to the direction of movement of the piston, in the recess of the cylinder. The control lines are accessible through threaded connections in a side extending parallel to the displacement direction of the piston.
The sealed displacement of the piston rod in the cylinder is attained in accordance with one embodiment of this invention where the piston rod is sealed by a sealing element which is maintained by a closing element in a widened shoulder of the bore in the cylinder for receiving the piston rod.
The function of the cylinder as a fastening element is simply achieved where the cylinder has, outside of the piston-cylinder unit in the end section facing away from the bearing bracket, a fastening receptacle, T-shaped in cross section, in which a threaded bore for receiving a fastening screw ends.